Sleep spindles.

Sleep spindles are discussed from various viewpoints. The definition of this pattern has been debated and requires clarification. There is evidence of two spindle types around 14 c/s and 12 c/s. The existence of a third spindle type (around 10 c/s) is controversial. The relationship of spindles to vertex waves and K complexes and the role of spindles in sleep staging are other topics that are covered. As "transient nonstationarities," spindles may escape methods of EEG computer analysis; special methods of spindle detection have been designed. Spindle activity may be influenced by various sedative drugs. An exceptional coexistence of spindles and waking patterns may occur in patients with 5-HIAA-hypersomnia. Sleep spindles change with age and show a typical configuration in early childhood; their decline in old age is also discussed. In monkeys and apes, "natural" spindle activity declines after adolescence. The distinction between natural and experimentally induced (barbiturate) spindles in animals must be stressed. After a discussion of spindle anomalies in neurological diseases, depth EEG data are presented. Spindles are found in the frontal cortex, whereas the scalp EEG indicates light drowsiness or even wakefulness. Attempts are made at an integrated view of these findings. A "shock-absorbing" function is attributed to spindles.